To find the width of the fish tank, we can use the formula for the volume of a rectangular prism:
\[ \text{Volume} = \text{Length} \times \text{Width} \times \text{Height} \]
Given that the volume is 1,920 cubic inches, the height is 12 inches, and the length is 20 inches, we can rearrange the formula to solve for the width:
\[ \text{Width} = \frac{\text{Volume}}{\text{Length} \times \text{Height}} \]
Substituting the known values into the formula:
\[ \text{Width} = \frac{1920}{20 \times 12} \]
Calculating the product of the length and height:
\[ 20 \times 12 = 240 \]
Now we can substitute this back into the equation for width:
\[ \text{Width} = \frac{1920}{240} \]
Now, we can perform the division:
\[ \text{Width} = 8 \]
Thus, the width of the tank is 8 inches.